The invention relates to a spindle lock of a hand-held combination drill and chisel hammer comprising a gearbox, a countershaft rotatably supported in the gearbox about an axis of rotation, and a locking plate that is guided in guide means within the gearbox parallel to the axis of rotation, wherein the movable locking plate is provided for selectively locking and releasing rotational movement of the countershaft.
A similar spindle lock is disclosed in DE 10 2004 052 329 A1 in which however the tool spindle and not the countershaft can be locked directly by means of a locking plate.
Hand-held combination drill and chisel hammers are operated in different working modes depending on the application. As selected by the operator, the drive motor of the hammer device can either provide purely a rotational movement of the tool spindle for drilling operation, can exclusively drive the hammer action without rotational movement of the tool spindle for providing purely a chiseling operation, or can provide a combined rotary and chisel drive action. For generating purely a chiseling operation, it is necessary to lock the tool spindle in the rotational direction. Such a locking action is usually provided by locking, as needed, the countershaft that is provided for driving in rotation the tool spindle.
In such a prior art spindle lock, a locking plate is provided that is guided slidably in the gearbox parallel to the axis of rotation of the countershaft. The locking plate has a section that surrounds the countershaft and this section is provided with teeth that are pushed upon axial displacement into gaps between teeth of a pinion on the countershaft. The locking plate that is fixedly connected to the gearbox housing prevents in this position a rotational movement of the pinion that is rotatably supported on the countershaft and therefore also a rotational movement of the tool spindle that is driven by it.
In prior art devices, guide pins are inserted into the gearbox housing for providing the axially displaceable guiding action of the locking plate; the locking plate is slidable on the pins by means of suitable guide openings. A precise assembly of the guide pins taking into account the required strength is difficult and complex. After mounting of the guide pins has been completed, the locking plate is pushed against a pretension of a spring onto the guide pins. This mounting step is also complex and costly because the guide plate must be secured in position against the pretension force of the spring until additional assemblies that are subsequently mounted take over this securing or fixation function.